Support background imagery from Editor Layer Index

[andrewharvey]

Use case When solving quests and adding new data, it's incredibly valuable to have background imagery enabled. It helps users ensure they are matching the map feature to the correct real world feature, and it allows new data to be placed more accurately.

Currently we use ESRI World Imagery as a default and allow the user to manually select their own background imagery.

Proposed Solution However some location have more recent and higher resolution imagery which is already maintained at https://github.com/osmlab/editor-layer-index. It would be beneficial to allow users to swap to an imagery layers from the ELI via a list, based on the imagery available at their location. Potentially even using the layers flagged best as the default.

I suggest a new entry under "Toggle aerial / map background" for "Choose aerial", which presents a list of imagery from ELI at the current location.

I would also suggest to allow the ELI imagery index URL customisable for advanced users.

[rusty-snake]

I guess this depends on #525. ELI seems to have a lot WMS.

[andrewharvey]

I guess this depends on https://github.com/Helium314/SCEE/issues/525. ELI seems to have a lot WMS.

I wouldn't say it depends on #525 since at a minimum XYZ sources can be implemented.

Besides many of the WMS services are entered into ELI not as the WMS endpoint, but rather a direct URL where you can pass a web mercator bbox and get tiles back. Since iD doesn't support true WMS either ELI tries as much as possible to do this.

MapLibre I believe can do sources like https://maplibre.org/maplibre-style-spec/sources/#raster with a URL of

http://a.example.com/wms?bbox={bbox-epsg-3857}&format=image/png&service=WMS&version=1.1.1&request=GetMap&srs=EPSG:3857&width=256&height=256&layers=example

MapLibre should then make requests for the XYZ tile bbox and get back the same XYZ tiles as an XYZ tile endpoint. Many WMS sources in ELI take this form.

EDIT: sorry I see #525 is asking for {bbox-epsg-3857} not full WMS support.

[andrewharvey]

EDIT comment moved to https://github.com/Helium314/SCEE/issues/525#issuecomment-2687534329